A Chinese court has handed down a 10-year jail sentence to Chen Xi, the second dissident in four days to be convicted of inciting subversion through online essays.

Another democracy campaigner, Chen Wei, was sentenced to nine years on 23 December. The two men are not related.

It is one of the heaviest sentences for inciting subversion since the Nobel laureate Liu Xiaobo was jailed for 11 years on Christmas Day 2009.

Arrests and detentions have gathered pace this year as the Communist party reacted to online calls for protests like those that have toppled dictators across the Middle East. The calls, however, have drawn little response and no large-scale protests have taken place in China.

The intermediate people's court in Guiyang, in south-west China's Guizhou region, tried Chen Xi, 57, on charges linked to more than 30 political essays he published online.

"The judge said this was a major crime that had a malign impact," his wife, Zhang Qunxuan, told Reuters by phone after the trial. The judge said Chen was a repeat offender who deserved a long sentence, she added.

Chen has insisted he was innocent, but will not appeal. "The court ignored all the points raised by the defence lawyer at the trial, so what point is there in appealing?" said Zhang.

He was detained on 29 November after campaigning for independent candidates to win seats in upcoming elections to the local People's Congress. His family were given notice of the trial on Saturday.

Chen is a leading member of the Guizhou Human Rights Forum, which has been declared an illegal organisation, according to Amnesty. The former factory worker was first jailed in 1989 for supporting student protests in Tiananmen Square, then served a second, 10-year jail term from 1995 to 2006.

Both he and Chen Wei signed Charter 08, which urges political reforms. Chen Wei also took part in the 1989 student movement. He was sentenced in Suining, Sichuan province, for incitement to subversion relating to four essays online.

Beijing's nervousness about criticism has led to tighter online controls. On Sunday Shanghai became the latest large city to order Chinese tweeters to register their real names when opening accounts, the Xinhua news agency reported.

Twitter is banned in China but lively debate, cynical jokes and criticisms of official corruption spread rapidly on home-grown services such as Sina Weibo. The decision applies to new users from Monday, and will eventually cover all users. The new real-name registration rules were first applied in Beijing on 16 December, then expanded to Guangzhou and Shenzhen.

The EU ambassador to Beijing, Markus Ederer, said on Saturday that the EU was "deeply concerned" about the nine-year sentence given to Chen Wei. "The EU firmly upholds freedom of expression as a universal human right and we encourage political debate rather than the use of criminal law as a means to resolve diverging political opinions," Ederer said.